Bacterial infections have one of the extensive impacts on public health. Therefore, finding compounds with antibacterial properties could serve as an effective method. A nanocomposite, Ag/CaO was prepared from silver nitrate and egg shells. After calcination of egg shells, the remaining solid, CaO was cooled, then silver nitrate was added and the mixture was ground to a fine powder, and finally heated to 300 ^◦C. The brown solid obtained was characterized by XRD, SEM and XRF methods. The prepared Ag/CaO was exmained for antibacterial activity against gram-positive and gram-negative bacteria including keleb pneumonia, staphylococcus aureus, Esherichia coli. This work has a similar paper published in 25^th ECSOC 2021, but now we made two changes including the amount of silver nitrate and calcium oxide in the synthesis route, and the size of the first synthesized nanocomposite by grinding with a ballmill, and then we examined these two substances against the bacteria. In fact, changing the amount of silver, known as the antibacterial metal, was compared to the changing the size of the nanocomposite, which could have more antibacterial effect.